Question

Consider a ball rolling down an inclined plane. The normal force on the ball is what?

Answer 1

it will be perpendicular to the plane's slope.

Answer 2

As there is no acceleration of the centre of mass perpendicular to the plane, the corresponding net force is zero.
Hence normal force equals weight times cosine of the angle.

Answer 3

mgsinx

Answer 4

@rvgupta
What you have just written is the component of weight ALONG the plane, not NORMAL to it.